The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the inventors hereof, to the extent the work is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted to be prior art against the present disclosure.
A traditional recording system stores data to a hard disk drive (HDD) on multiple tracks that each have guard bands on either side of the track to help prevent unintentional overwriting of the data. Each track is further divided into randomly accessible sectors, which are protected by sector-level error correction codes.
In shingled magnetic recording (SMR), the track pitch is made arbitrarily small, and guard bands are reduced or removed to increase track density. In particular, in SMR, data are stored on partially overlapping tracks that interfere with one another. Accordingly, in such systems data must be written to the HDD on a track-by-track basis. That is, writing data to only a specific sector of a given track of the HDD requires rewriting a given track or a band of sequentially overlapping tracks in its entirety.
Furthermore, in an HDD, different codewords or sectors often experience different noise characteristics or different noise realizations, even if the statistical properties of the noise is the same across the HDD. Thus, some portions of a track may be more prone to errors while other portions are less prone to errors.